The present invention relates to novel copolyamide fibers having an excellent initial modulus of elasticity and mechanical strength.
U.S. Pat. No. 4,178,431 for T. Kaneda et al, discloses a fiber composed of a high molecular weight copolyamide which is a copolymerization product of a diamine component consisting of a mixture of benzidine sulfone and p-phenyldiamine with a dicarboxylic component consisting of terephthalic acid or its reactive derivative. This type of copolyamide fiber exhibits an excellent initial modulus of elasticity and mechanical strength. However, the fiber is disadvantageous in that the copolyamide from which the fiber has been made, contains, as a portion of the diamine component, benzidine sulfone which per se is mutagenic and, also, which has been usually prepared from benzidine that is carcinogenic. That is, benzidine is not allowed to be industrially used for producing benzidine sulfone, and also, using benzidine sulfone for producing the copolyamide should be avoided.
Under the above-mentioned circumstances, it was strongly desired to provide a new type of aromatic copolyamide fiber which exhibits an excellent initial modulus of elasticity and mechanical strength similar to those of the benzidine sulfone-containing copolyamide fiber and which can be prepared by using a diamine component which is neither mutagenic nor carcinogenic.